This invention relates to the programming of a central receiving unit to identify sending units such as radio-frequency tire pressure sending units associated with a vehicle.
U.S. Pat. No. 5,600,301, assigned to the assignee of the present invention, discloses a tire pressure monitoring system that includes sending units associated with each tire of a vehicle and a central receiving unit. Each of the sending units includes a respective radio-frequency transmitter that transmits an RF signal including both an identifier code and an indicator of tire pressure. Additionally, each of the sending units includes a magnet sensor. When the receiving unit is placed in a learn mode, a magnet is used to activate each sending unit of the vehicle in a predetermined order. The receiver learns the identifiers associated with the respective tires based upon the sequence of activation of the sending units. This approach has been found reliable in use, but it requires the user to have a suitable magnet for sequentially activating the sending units.
U.S. Pat. No. 5,731,516 describes a receiver that identifies transmitters associated with a vehicle by first recording the identification codes received from the transmitters. After recording the identification codes, the receiver verifies that the identified transmitters are installed on the vehicle by insuring that tire data is also received from the previously-identified transmitters.
One problem of the prior art is that physically adjacent vehicles may include sending units that transmit similar identification codes and pressure indicators on the same or a similar frequency. In this event the receiver can mistakenly record the identification code from an adjacent vehicle, instead of the desired identification code associated with the vehicle in which the receiver is mounted.